and abundance of aerobic and selleck screening library anaerobic methane oxidizers at the Haakon Mosby mud volcano, Barents Sea. Appl Environ Microbiol 2007,73(10):3348–3362.PubMedCrossRef 33. Manz W, Eisenbrecher M, Neu TR, Szewzyk U: Abundance and spatial organization of Gram-negative sulfate-reducing bacteria in activated sludge investigated by in situ probing with specific 16S rRNA targeted oligonucleotides. FEMS Microbiol Ecol 1998,25(1):43–61.CrossRef Authors’ contributions YZ carried out the incubation and DAPI staining, participated in CARD-FISH and drafted the manuscript. LM carried out the CARD-FISH and participated Endonuclease on the sequence analysis. XZ and FW carried the clone libraries and sequence analysis. NB conceived of the study, and participated in its design and coordination and helped to draft the manuscript. All authors read and approved the final manuscript.”“Background DNA strands in most prokaryotic genomes often experience strand-biased spontaneous mutations, especially in protein coding regions, which occur preferentially in the leading strand during DNA replication [1, 2]. It has been found that the directions of GC skew often change at flanking regions around bacterial replication origins [[3–8]].